Whether reports of iPhones overheating are entirely true or not, Apple seems to be taking the situation seriously enough to reveal the presence of a temperature warning screen for the iPhone 3G and 3GS.

According to Gearlog, an unknown but probably very small number of iPhones have been affected by overheating, to the point that some white iPhone 3GSes have allegedly turned pink.

Apple, has issued what some might call a “common sense” warning: a support document that warns users not to keep the iPhone in an environment where temperatures can exceed 113 degrees Fahrenheit, including parked cars.

The company has also warned that CPU-intensive applications, such playing music or using the GPS while in direct sunlight may also overheat the iPhone.

In that case, actually using the iPhone in temperatures over 95 degrees can also trigger the temperature warning. “Low- or high-temperature conditions might temporarily shorten battery life or cause the device to temporarily stop working properly,” Apple warns.

Apple also says that the iPhone 3G and 3GS should not be stored where the temperature can fall under -4 degrees Fahrenheit, or used in less in temperatures under 0 degrees F.

If the phone exceeds those temperatures, Apple says, the iPhone may stop charging, its display might dim, a weak cellular signal may be experienced, and the temperature warning screen on the left may also appear. Apple’s support document implies that there’s a temperature sensor of some sort built in to the iPhone 3G or 3G S

Stay tuned for additional details as they become available and please let us know if you’ve seen this on your end.